|Toshiba A (left) and RCA PB144 ribbon microphones|
The microphone on the left is generally know in internet-land as the Toshiba ‘Type A’, although it is labelled SN-1631. It is a very close copy of the RCA 44A and its relatives. I have been informed by a Japanese expert that this was made under license by RCA, most likely in the post-WW2 era. Having looked carefully at the Type A and compared it to my own RCA PB144 (right), I have no reason to doubt this assertion.
The mics look similar outside – my PB 144 has a film set style hanger mounting, whist the Toshiba has a simple cast yoke, and the grill hole size differs.
Inside the microphones there are many similarities and few differences. Both use three large horseshoe magnets to provide the magnetic field, and and the ribbon dimensions are very close.